Calculator
Enter any two variables. Select the target value to calculate. The selected result appears above this form after submission.
Plotly Graph
This chart shows how torque changes with speed for the resolved power level. It helps compare low-speed and high-speed operating points quickly.
Formula Used
Power = Torque × Angular Speed
Torque = Power ÷ Angular Speed
Angular Speed = Power ÷ Torque
Delivered Power = Input Power × Efficiency
Torque (N·m) = 9550 × Power (kW) ÷ Speed (RPM)
Angular speed in rad/s equals RPM × 2π ÷ 60. The calculator converts selected units internally, applies efficiency, then returns the answer in your chosen output unit.
How to Use This Calculator
- Select whether you want to solve for torque, power, or speed.
- Enter the two known values and choose matching units.
- Set efficiency if transmission losses should be considered.
- Choose the number of decimal places for the report.
- Press Calculate Now to show the result above the form.
- Use the CSV and PDF buttons to export the current calculation.
- Review the graph to see torque behavior across changing speed.
Example Data Table
| Case | Known Inputs | Calculated Result | Notes |
|---|---|---|---|
| Motor A | 5 kW, 1500 RPM | 31.831 N·m | Classic motor torque estimate. |
| Motor B | 10 hp, 1750 RPM | 30.012 lb-ft | Imperial unit comparison. |
| Drive C | 3.2 kW, 300 rad/s | 10.667 N·m | High speed, lower torque case. |
| Reducer D | 120 N·m, 1800 RPM | 22.619 kW | Power requirement from torque demand. |
FAQs
1. What does this calculator solve?
It solves the relationship between power, torque, and rotational speed. You can calculate any one of the three when the other two are known.
2. Why is torque higher at lower speed for the same power?
Because torque and speed are inversely related when power stays constant. As speed drops, more torque is required to deliver the same mechanical power.
3. What is the role of efficiency?
Efficiency accounts for mechanical or transmission losses. Lower efficiency means more input power is needed, or less torque is delivered to the shaft.
4. Can I use horsepower instead of watts?
Yes. The calculator accepts watts, kilowatts, megawatts, and horsepower. It converts everything to a common internal base before calculating.
5. Which torque units are supported?
You can work with N·m, lb-ft, and lb-in. This makes the tool useful for both metric and imperial engineering workflows.
6. Why is angular speed shown in rad/s and RPM?
The fundamental equation uses angular speed in rad/s. RPM is shown because it is more familiar in machine design, motors, and rotating equipment work.
7. When should I use the shortcut 9550 × kW ÷ RPM?
Use it when power is in kilowatts and speed is in RPM. It directly gives torque in N·m and is widely used for quick engineering checks.
8. Is this useful for motors, gearboxes, and pumps?
Yes. It is useful for motors, fans, conveyors, reducers, shafts, and other rotating systems where power-speed-torque relationships affect sizing and selection.